Reseal Tubeless Mountain Bike Tires: A Quick Guide

Last Updated on October 25, 2026 by Jaxon Mike

Yes, you can absolutely reseal tubeless mountain bike tires yourself! It’s a manageable DIY project that can save you money and keep your tires running smoothly. You’ll need a few basic supplies and a little patience to get your tubeless setup holding air again.

Many riders find their tubeless tires lose pressure over time. This is often due to dried-out sealant or a tiny leak. Knowing how to reseal them means you can avoid costly shop visits and get back on the trail faster. We’ve researched the common issues and found simple solutions.

• Check for leaks first.
• Add fresh sealant.
• Ensure the bead is seated correctly.
• Reinstall your valve core.
• Spin and shake the wheel to distribute sealant.

Ready to get your tires back in top shape? Let’s walk through exactly how to reseal your tubeless mountain bike tires step by step.

Keeping Your Tubeless Tires Inflated

It’s a common frustration: you set up your tubeless tires perfectly, and they work great for a while. Then, slowly, they start to lose air. Don’t worry, this is usually a sign that your sealant needs a refresh, not that your tires are ruined. You can absolutely reseal your tubeless mountain bike tires yourself with a few simple steps. This guide will help you get your setup holding air again, so you can get back to enjoying your rides.

Troubleshooting Air Loss in Tubeless Tires

Before you add more sealant, it’s wise to figure out where the air is escaping. Sometimes, the problem isn’t just dried sealant. We’ve found that a quick check can save you a lot of hassle.

Finding the Leaks

Your first step is to find the source of the leak. This is often easier than you think. You’ll want to listen for hissing sounds. If you can’t hear anything, you can try the soapy water trick.

The Soapy Water Method

Mix a good amount of dish soap with water in a spray bottle or a bucket. Apply this mixture generously to your tire. Look for bubbles forming anywhere on the tire or rim. Bubbles mean air is escaping there. Pay close attention to the valve stem area and the tire bead where it meets the rim. These are common spots for leaks. Even a tiny pinhole in the tire can be found this way.

Assessing the Sealant’s Condition

Sealant is what keeps your tubeless setup airtight and seals small punctures. Over time, it dries out. If your tires are losing air quickly, your sealant might be the culprit.

Signs of Dry Sealant

When you remove your tire, you’ll likely see a dried, crusty layer on the inside. This is old sealant that has done its job but is no longer liquid enough to seal. Many experts suggest that sealant typically lasts 3 to 6 months, depending on your climate and riding conditions. Hot, dry weather can dry it out much faster (MTB Mag).

Adding Fresh Sealant to Your Tires

Adding new sealant is the most common way to reseal your tubeless tires. There are a couple of ways to do this, but one is generally easier than the other.

The Easiest Method: Through the Valve Stem

This method allows you to add sealant without removing the tire from the rim. It’s much cleaner and quicker.

What You’ll Need

• Fresh tubeless sealant
• A sealant injector or a syringe with a small hose
• A valve core removal tool (often built into a valve cap or a separate small tool)

Steps for Adding Sealant

1. Remove the Valve Core: Use your valve core removal tool to unscrew the valve core. This will let the sealant flow in easily. Be careful not to lose the tiny core!
2. Inject the Sealant: Attach your syringe or injector to the valve stem. Measure out the recommended amount of sealant. Most manufacturers suggest 2-4 ounces for mountain bike tires, but check your sealant’s instructions. Slowly inject the sealant into the tire.
3. Reinstall the Valve Core: Once the sealant is in, carefully screw the valve core back into the valve stem. Tighten it gently but firmly.
4. Inflate the Tire: Now, inflate your tire to your desired riding pressure.

Alternative Method: Pouring Sealant into the Tire

This method involves removing the tire bead from the rim. It’s a bit messier but can be useful if you need to thoroughly clean out old sealant or inspect the tire inside.

Steps for Pouring Sealant

1. Deflate the Tire: Let all the air out of your tire.
2. Break the Bead: Carefully push the tire bead down into the center channel of the rim on one side. You might need to use your hands or a tire lever.
3. Pour in Sealant: Pour the recommended amount of fresh sealant directly into the tire cavity.
4. Reseat the Bead: Work the tire bead back onto the rim. You may need to use a tire lever for this.
5. Inflate: Inflate the tire. You’ll likely hear it pop into place as the bead seats.

Ensuring a Good Seal and Distributing Sealant

After adding sealant and inflating, the job isn’t quite done. You need to make sure everything is sealed up tight and the sealant is spread evenly.

Checking for Leaks Again

Go back to the soapy water method if you suspect leaks. Spray down the tire and rim again. If you see any bubbles, try to locate the source. Sometimes, just spinning the wheel can help the sealant find the small leak and seal it.

Distributing the Sealant Properly

This is a crucial step that many people overlook. You need to get that liquid sealant coating the entire inside of your tire.

The Shake and Spin Technique

Hold your wheel and spin it in circles. Then, tilt it side to side, letting the sealant move to different parts of the tire. Do this for a few minutes. This ensures the sealant coats the bead and the entire inner surface, ready to seal any small gaps or punctures. We’ve found that a good minute or two of vigorous shaking and spinning is usually sufficient.

Common Issues and How to Address Them

Even with fresh sealant, you might encounter a few hiccups. Knowing these can help you solve them quickly.

The Tire Won’t Seat Properly

Sometimes, the tire bead just won’t pop into the rim. This can be due to old dried sealant gumming up the rim channel, or the bead being stiff. Try removing the valve core to allow maximum airflow. A blast from a compressor or a CO2 inflator can help seat stubborn beads. Sometimes, adding a little more soapy water to the tire bead can help it slide into place.

Persistent Leaks at the Valve Stem

If you still see bubbles around the valve stem, it might be loose or damaged. Ensure the valve nut (if your wheels have one) is snug. If the valve itself is old or cracked, it might be time to replace it. A leaky valve core can also be the cause; try replacing just the core first.

Sealant Leaking Through Tire Sidewalls

Some tires are more porous than others, especially lighter XC or gravel tires. You might see a fine mist of sealant weeping through the sidewalls. This is often normal and should seal up after a few rides. Keep spinning and shaking your wheels to help it along. If it’s a steady drip, you might have a larger issue or need a more robust sealant formulation (Stan’s NoTubes).

Sealant Dos and Don’ts Checklist

Here’s a quick rundown to make sure you’re doing it right:

• DO use the recommended amount of sealant for your tire size.
• DO shake your bottle of sealant well before using.
• DON’T let your sealant dry out completely inside the tire.
• DO check your sealant levels every few months, especially in hot weather.
• DON’T over-tighten the valve core when reinstalling.
• DO spin and shake your wheel to distribute sealant after adding it.

Conclusion

You’ve got this! Resealing your tubeless mountain bike tires is a straightforward process that puts maintenance power back in your hands. By understanding how to find leaks, add fresh sealant, and properly distribute it, you can keep your tires holding air and performing their best. Don’t let a slow leak keep you off the trails. Grab your sealant and tools, and take charge of your tubeless setup today.

Frequently Asked Questions

How often should I check my tubeless sealant level?

We recommend checking your sealant levels every 3 to 6 months. In hotter, drier climates, or if you ride frequently in abrasive conditions, you might need to check more often, perhaps every 2 months. This ensures the sealant remains liquid and effective at sealing punctures.

Can I use any type of sealant in my tubeless tires?

It’s best to use a sealant specifically designed for tubeless bicycle tires. Different formulations have varying effectiveness against different puncture sizes and can interact differently with tire and rim materials. Always check the manufacturer’s recommendations for your tires and rims.

My tire is losing air slowly, but I don’t see bubbles with soapy water. What else could it be?

Slow air loss without visible bubbles often points to a very small leak or dried sealant that isn’t coating the inside of the tire properly. Ensure you’ve shaken and spun the wheel vigorously to distribute the sealant. It could also be a porous tire sidewall, which is common and often seals with riding.

Is it normal for some sealant to weep through the tire sidewall?

For some lighter-weight or less dense tire casings, a small amount of sealant weeping through the sidewalls can be normal. This usually seals up after a few rides as the sealant gets distributed. If it’s a steady drip rather than a mist, you might have a more significant issue.

How much sealant do I need to add to my mountain bike tires?

The amount varies by tire size, but for most mountain bike tires, 2 to 4 ounces (60-120 ml) of sealant is a good starting point. Always refer to the sealant manufacturer’s guidelines for their specific product and your tire volume to avoid using too little or too much.